The present invention concerns the assembly of a rail of a railway track on a rigid support and more particularly the assembly on a concrete sleeper of a long welded rail.
Because of the harsh forces and vibrations which rails must withstand, it is necessary to interpose between the rail and its support an elastic liner, generally of rubber, having a flexibility which permits displacement of the rail with respect to its support. The rail is thus maintained on this support by springs, known as elastic clips, which deform to absorb all its vertical movements. There remain however horizontal components of rail movements which cause wear of the rail and of its clips. It has therefore been considered to dispose, between the clip and the rail, a resilient rail restraining member. As this rail restraining member contributes equally to, on the one hand, electric insulation of the rail and, on the other hand, maintenance of an exact positioning of the rail on the support, it is generally formed of a plastic non-conducting material simultaneously presenting good mechanical strength and electrical resistance while being sufficiently elastic.
Unfortunately, the known rail restraining--or more precisely the systems of elastic clips and rail restraining members known to date--are not wholly satisfactory. For example, it has been found that the rail restraining members often break and that they only partially prevent the phenomenon of tramping of the rail and that the known systems can only be used for the mounting of short lengths of rail, of tunnel trackway or the like. In fact, the positioning of long welded rail, which is the general practice on main lines, can only be achieved in certain temperature conditions for avoiding excessive stresses in the rails by virtue of thermal expansion. When the ambient temperature is too low, it is necessary to heat the rails with the aid of burners. None of the conventional materials used for the rail restraining members can resist the heat generated by the flame of these burners and it is for this reason that on long welded rail the use of resilient liners and rail restrainers is not generally possible.